"Reports indicate there have been more than 45 new detentions of Baha'is in the last four months alone, and currently as many as 60 Baha'is are imprisoned in Iran solely on the basis of their religious beliefs," the state department noted.

"Authorities also detained more than a dozen Christians, some of whom are being held in custody without substantiated charges," it continued.

Presently, Iran's constitution identifies Islam as the official state religion and recognizes Christians, Jews, and Zoroastrians as "protected" religious minorities.

Despite the protected status, non-Shi'a Muslims in practice face discrimination and the government severely restricts freedom of religion, according to the U.S. Department of State's 2009 International Religious Freedom Report.

Last month, the 31st anniversary of Iran's Islamic Revolution was marred by protests and criticism of religious abuse.

Civilians took to the streets to demonstrate against the current hard-line government led by President Mahmoud Ahmadinejad, but were blocked by security forces as they marched toward Tehran square.

On the eve of the anniversary of the Islamic Revolution, the U.S. Commission on International Religious Freedom released a statement condemning the Iranian government's harassment of its citizens over their religious adherence and noted how the government in recent years has stepped up persecution of religious minorities, including Christians, who face physical attacks, harassment, detention, arrests and imprisonment.

"Sadly, the Iranian government has been repressing its citizens on the basis of religious identity for years, but in recent months it has been increasingly manipulating the reach of its religious laws to silence, and in some cases put to death, Shia Muslims simply for exercising their internationally protected rights of freedom of expression and freedom of thought, conscience, religion, or belief," reported USCIRF Chair Leonard Leo.

Since 1999, the U.S. Department of State has designated Iran a "Country of Particular Concern" – a label reserved for countries with the most severe abuses of religious freedom.

In its statement Friday, the State Department highlighted Iran's pledge last month to abide by international law and said it was "deeply disappointed" by its failure to put an end to religious discrimination.

"We join the international community in urging Iran to uphold its obligations to protect the human rights and fundamental freedoms of all its people," the department concluded.

According to estimates, non-Muslims account for about two percent of the population.